Americans find it hard to imagine that the two-party system could ever break down. "Democracy works, this country works when you have two parties that are serious and trying to solve problems," President Barack Obama said recently. Yet U.S. democracy and the country itself would be better served if politicians started acting as if there were more parties -- which might be the case after this year's election.

Americans have laughed at me when I suggested that their two-party system might be giving way to a more European-style one. Yet foreigners like myself, used to multiparty parliaments and coalition governments, are not the only ones who see the U.S. moving toward this model. Jeffrey Sachs, the Columbia University professor, one of the architects of Poland's successful post-Communist transformation, wrote this week as calls multiplied for Senator Bernie Sanders to drop out of the Democratic race:

By 2020, it is quite possible that we will actually have four major political parties: a social democratic left, a centrist party, a right-wing conservative party and a populist anti-immigrant party (represented by Trump followers).

Where Sachs sees four parties, I see five: Sanders's socialists, Hillary Clinton's center-left, a center-right party for the likes of Governors John Kasich and Jeb Bush and Senator Marco Rubio, a conservative Christian party led by Senator Ted Cruz and Trump's right-wing populist force. Whether it's four parties or five, however, it's definitely not two: There are more distinct constituencies and more ideologies in U.S. society than the current system recognizes.

Yet the political machinery and the behavior of presidential candidates is based on the rigidity of a two-party system. Politicians are supposed to fall in step behind their parties' nominees. This is causing agony for some Republicans. House Speaker Paul Ryan had just endorsed Trump through clenched teeth when the presumptive nominee went after a judge because of his ethnicity; Ryan had to admit that the candidate's remarks fit "the textbook definition of a racist comment" -- but he couldn't bring himself to claw back the endorsement. Rubio, asked whether he still believed, as he'd said on the stump, that Trump couldn't be trusted with the U.S. nuclear codes, said he stood by all he'd said during the campaign but that he'd still vote for Trump because he'd signed a pledge to support the Republican nominee.

Trump appears to believe that now that he's on track to be the nominee, other Republicans owe him fealty. Kasich recalled a recent conversation with Trump: "Mr. Trump called me and said, 'What are you going to do to support me?'" The Ohio governor didn't feel compelled to do anything at all.

On the Democratic flank, Sanders is similarly expected to endorse Clinton without preconditions: He has lost, after all, so he should take it like a man and keep the party together in the face of the Trump threat. Well, perhaps he should be offered a few lines in the Democratic Party platform -- a document that means little because it is not linked to anyone's immediate executive or legislative agenda -- as a consolation prize.

It doesn't work like that in Europe, of course. After a parliamentary election, if the winner needs to form an alliance with some of the losers to secure a majority, there's no expectation that the parties closest to the winner in the political spectrum will automatically fall into line without expecting anything in return. Sometimes, the alliances that are made transcend ideological lines; they are formed by political forces that are the best at reaching compromises.

European politics can get messy, and sometimes -- as in Spain today -- there is no way to form a working government. Yet a standoff between the legislature and the executive branch, like the one that has lasted for most of Obama's two terms, is impossible. The ruling coalitions actually get to legislate and implement their compromise agendas.

Here's a hypothetical situation. Let's imagine a European-style parliamentary election in the U.S., with five parties taking part. Clinton's party wins a plurality. Trump's populists come in a close second. An alliance with either Sanders' socialists or the right-of-center moderates (Kasich, Rubio, Ryan) would give Clinton a majority. Trump would go over the top if he made a deal with the moderates and with Cruz's religious right (Sanders won't talk to Trump), and he'd have the majority, edging out Clinton and Sanders.

It would be quite conceivable that Clinton would go with the moderates to deny Trump a victory, and a centrist coalition would run the U.S. just as similar right-left cabinets run Germany and Austria today. There would be no overtones of betrayal, none of the current "if you're not for the Republican nominee, you're helping the Democratic one" binary calculus.

And the U.S. would have a workable, non-gridlocked political system for the next election cycle.

Sachs, of course, may have an axe to grind in predicting the Europeanization of the U.S. system by 2020. He wants Clinton to assign cabinet posts to the Sanders faction, the way she would have had to do in a European-style coalition. As Sanders's informal foreign policy adviser, the professor is not exactly disinterested when he makes this suggestion. It still makes sense though. Giving Sanders some power in the next government would mobilize his supporters for Clinton, whom they distrust, and it might keep them from defecting to Trump, the only remaining anti-establishment candidate.

Similarly, instead of expecting automatic loyalty, Trump would do better to coordinate agendas with the moderates and cede certain issues to them, which might make some of the doubts about his qualifications irrelevant.

Inertia is strong in U.S. politics, however. The main players continue pretending there are still only two relatively cohesive parties, which is no longer the case. The primary winners will act in the usual winner-take-all manner, alienate the potential supporters of likely coalitions and make it more difficult for themselves to win. Then the winner will represent significantly fewer than half of all voters because many won't turn out or will vote reluctantly. And there will likely be gridlock again.

If there's anything this election should have told U.S. politicians, it's that the traditional system is breaking down. There's no need to change the Constitution to accommodate a new multiparty reality. Unlike in Europe, the coalition deals would just need to be made after multiparty primary votes that the states could organize the way some of them run one-party primaries today. Then, ready-made, transparent coalitions would compete in national elections.

It's OK for rules to evolve if the evolution leads to better outcomes. The U.S. is great at embracing technological innovation; political innovation shouldn't be ruled out, either.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.